1. Field of the Invention
The present invention relates generally to a Digital Rights Management (DRM) method and system for content copyright protection, and more particularly to a DRM method and system for content copyright protection which can protect right information on DRM content and effectively manage the right information.
2. Description of the Prior Art
Recently, copyrights protection technologies, such as DRM, have been developed to protect the copyrights on digital content, including music, images and computer games, distributed through the Internet or digital broadcasting by restricting the number of reproductions, transfer and copying of the content.
FIG. 1 is a view showing time synchronization in a conventional Code Division Multiple Access (CDMA) network which includes a base station 10 for sending a pilot signal, devices (e.g., mobile stations) 21 and 22 for receiving the pilot signal from the base station 10 and consuming content, and a Global Positioning System (GPS) 30 for sending a standard time synchronous with a Universal Time Coordinated (UTC) to the base station 10. The pilot signal includes information necessary for time calculation in the devices 21 and 22.
In the conventional CDMA network, the base station 10 synchronizes time through the GPS 30. Also, the devices 21 and 22 acquire time information from a pilot signal received from the base station 10 and perform the time synchronization.
Even if the device 21 and 22 arbitrarily change the time, it is possible to prevent the change by obtaining the time information from the base station 10. In the CDMA network, the devices 21 and 22 can confirm the effectiveness of a right to legally use the content. The “right” refers to right-to-use information that specifies a right to reproduce the content.
However, in a Global System for Mobile communication (GSM) network that provides no time synchronization protocol, users of the devices 21 and 22 can arbitrarily change the time to illegally use DRM content.
The following solutions can be considered to solve the above problems.
A first solution is to mount a separate timer in a device (e.g., a mobile terminal) to prevent any arbitrary change of time. The timer mounted in the device can preserve a time period of use which has been preset in the right information on the DRM content.
However, the separate timer for checking the time period of actual use will be a burden to the user as an addition of hardware to the device.
A second solution is to synchronize the time using a standard Network Time Protocol (NTP).
For the communication between the conventional time synchronization protocol and the NTP, an on-line connection is needed, which will also be a burden to the user. The second solution cannot be used in places where on-line connections are not possible.
Korean Unexamined Patent Application No. 2002-064672, entitled “Content Usage Management System and Method”, discloses a system and a method for managing the use of content by providing a license information processor that controls the use of the content according to right information transferred from a server to the user's device, which represents the user's right to use the content.
The disclosed techniques, however, do not solve the problems of the prior art requiring a separate on-line connection because the server should send a license ticket, which is an elementary unit constituting the user' right to use, to the user's device.